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741. Massive binaries in the LMC
ID:
ivo://CDS.VizieR/J/ApJ/748/96
Title:
Massive binaries in the LMC
Short Name:
J/ApJ/748/96
Date:
21 Oct 2021
Publisher:
CDS
Description:
The stellar mass-luminosity relation is poorly constrained by observations for high-mass stars. We describe our program to find eclipsing massive binaries in the Magellanic Clouds using photometry of regions rich in massive stars, and our spectroscopic follow-up to obtain radial velocities and orbits. Our photometric campaign identified 48 early-type periodic variables, of which only 15 (31%) were found as part of the microlensing surveys. Spectroscopy is now complete for 17 of these systems, and in this paper we present analysis of the first two, LMC 172231 and ST2-28, simple detached systems of late-type O dwarfs of relatively modest masses. Our orbit analysis yields very precise masses (~2%), and we use tomography to separate the components and determine effective temperatures by model fitting, necessary for determining accurate (0.05-0.07 dex) bolometric luminosities in combination with the light-curve analysis. Our approach allows more precise comparisons with evolutionary theory than previously possible. To our considerable surprise, we find a small, but significant, systematic discrepancy: all of the stars are slightly undermassive, by typically 11% (or overluminous by 0.2 dex) compared with that predicted by the evolutionary models. We examine our approach for systematic problems, but find no satisfactory explanation. The discrepancy is in the same sense as the long-discussed and elusive discrepancy between the masses measured from stellar atmosphere analysis with the stellar evolutionary models, and might suggest that either increased rotation or convective overshooting is needed in the models.
742. 2MASS large-amplitude variable stars
ID:
ivo://CDS.VizieR/J/AJ/138/1508
Title:
2MASS large-amplitude variable stars
Short Name:
J/AJ/138/1508
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of variable stars in the near-infrared wavelength detected with overlapping regions of the Two Micron All Sky Survey public images, and discuss their properties. The investigated region is in the direction of the Galactic center (-30{deg}<~l<~20, |b|<~20), which covers the entire bulge. We have detected 136 variable stars, of which six are already known and 118 are distributed in the |b|<5{deg} region. Additionally, 84 variable stars have optical counterparts in Digitized Sky Survey images. The three diagrams (color-magnitude, light variance, and color-color diagrams) indicate that most of the detected variable stars should be large-amplitude and long-period variables such as Mira variables or OH/IR stars. The number density distribution of the detected variable stars implies that they trace the bar structure of the Galactic bulge.
743. Mass loss from Miras with and without Tc
ID:
ivo://CDS.VizieR/J/A+A/622/A120
Title:
Mass loss from Miras with and without Tc
Short Name:
J/A+A/622/A120
Date:
21 Oct 2021
Publisher:
CDS
Description:
We follow-up on a previous finding that AGB Mira variables containing the third dredge-up indicator technetium (Tc) in their atmosphere form a different sequence of K-[22] colour as a function of pulsation period than Miras without Tc. A near- to mid-infrared colour such as K-[22] is a good probe for the dust mass-loss rate of the stars. Contrary to what might be expected, Tc-poor Miras show redder K-[22] colours (i.e. higher dust mass-loss rates) than Tc-rich Miras at a given period. Here, the previous sample is extended and the analysis is expanded towards other colours and dust spectra. The most important aim is to investigate if the same two sequences can be revealed in the gas mass-loss rate. We analysed new optical spectra and expanded the sample by including more stars from the literature. Near- and mid-IR photometry and ISO dust spectra of our stars were investigated where available. Literature data of gas mass-loss rates of Miras and semi-regular variables were collected and analysed. Our results show that Tc-poor Miras are redder than Tc-rich Miras in a broad range of the mid-IR, suggesting that the previous finding based on the K-[22] colour is not due to a specific dust feature in the 22-micron band. We establish a linear relation between K-[22] and the gas mass-loss rate. We also find that the 13 micron feature disappears above K-[22]~2.17mag, corresponding to dM/dt}_g_~2.6x10^-7^M_{sun}/yr. No similar sequences of Tc-poor and Tc-rich Miras in the gas mass-loss rate vs. period diagram are found, most probably owing to limitations in the available data. Different hypotheses to explain the observation of two sequences in the P vs. K-[22] diagram are discussed and tested, but so far, none of them convincingly explains the observations. Nevertheless, we might have found an hitherto unknown but potentially important process influencing mass loss on the TP-AGB.
744. 2MASS photometry of cataclysmic variables
ID:
ivo://CDS.VizieR/J/other/NewA/13.133
Title:
2MASS photometry of cataclysmic variables
Short Name:
J/other/NewA/13.
Date:
21 Oct 2021
Publisher:
CDS
Description:
Spatial distribution, galactic model parameters and luminosity function of cataclysmic variables (CVs) in the solar neighbourhood have been found using distances estimated from the period-luminosity-colours (PLCs) relation of CVs. It can be concluded that exponential function fits better to the observational z-distributions of the whole CVs in the sample, non-magnetic CVs and dwarf novae, while the sech^2^ function is more appropriate for nova-like stars and polars. The vertical scaleheight of CVs is 158+/-14pc for the 2MASS J band limiting apparent magnitude of 15.8. The discrepancies between the theoretical and observational population studies of CVs can be at least partly removed if the sech^2^ density function is used in deriving the galactic model parameters. We estimated the vertical scaleheights of 128+/-20pc and 160+/-5pc for dwarf novae and nova-like stars, respectively. The local space density of CVs is found ~3x10^-5^pc^-3^ which is in agreement with the lower limit of the theoretical predictions. The luminosity function of CVs shows a trend toward higher space density at low luminosity, implying an increase in the number of short-period systems.
745. Maxima of short period pulsating stars
ID:
ivo://CDS.VizieR/J/other/JAVSO/39.23
Title:
Maxima of short period pulsating stars
Short Name:
J/other/JAVSO/39
Date:
21 Oct 2021
Publisher:
CDS
Description:
This paper contains times of maxima for 56 short period pulsating stars (primarily RR Lyrae and delta Scuti stars). This represents a portion of the CCD observations received by the AAVSO Short Period Pulsator (SPP) section in 2010 along with some earlier data.
746. M31B eclipsing binaries and Cepheids
ID:
ivo://CDS.VizieR/J/AJ/115/1016
Title:
M31B eclipsing binaries and Cepheids
Short Name:
J/AJ/115/1016
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have undertaken a long-term project, DIRECT, to obtain the direct distances to two important galaxies in the cosmological distance ladder - M31 and M33 - using detached eclipsing binaries (DEBs) and Cepheids. While rare and difficult to detect, DEBs provide us with the potential to determine these distances with an accuracy better than 5%. The extensive photometry obtained in order to detect DEBs provides us with good light curves for the Cepheid variables. These are essential to the parallel project to derive direct Baade-Wesselink distances to Cepheids in M31 and M33. For both Cepheids and eclipsing binaries, the distance estimates will be free of any intermediate steps. As a first step in the DIRECT project, between 1996 September and 1997 January we obtained 36 full nights on the Michigan-Dartmouth-MIT Observatory 1.3m telescope and 45 full/partial nights on the F.L. Whipple Observatory 1.2m telescope to search for DEBs and new Cepheids in the M31 and M33 galaxies. In this paper, first in a series, we present the catalog of variable stars, most of them newly detected, found in the field M31B [({alpha},{delta})=(11.20{deg}, 41.59{deg}), J2000.0]. We have found 85 variable stars: 12 eclipsing binaries, 38 Cepheids, and 35 other periodic, possible long-period or nonperiodic variables. The catalog of variables, as well as their photometry and finding charts, is available via anonymous ftp and the World Wide Web: http://cfa-www.harvard.edu/~kstanek/DIRECT.
747. MC Cepheids, RR Lyrae stars and binaries
ID:
ivo://CDS.VizieR/J/MNRAS/437/2702
Title:
MC Cepheids, RR Lyrae stars and binaries
Short Name:
J/MNRAS/437/2702
Date:
21 Oct 2021
Publisher:
CDS
Description:
The VISTA near-infrared Y, J, Ks survey of the Magellanic System (VMC) survey is obtaining multi-epoch photometry in the Ks band of the Magellanic System down to a limiting magnitude of Ks~19.3 for individual epoch data. The observations are spaced in time such as to provide optimal sampling of the light curves for RR Lyrae stars and for Cepheids with periods up to 20-30d. We present examples of the Ks-band light curves of Classical Cepheids and RR Lyrae stars we are obtaining from the VMC data and outline the strategy we put in place to measure distances and infer the System three-dimensional geometry from the variable stars. For this purpose, the near-infrared Period-Luminosity, Period-Wesenheit and Period-Luminosity-Colour relations of the system RR Lyrae stars and Cepheids are used. We extensively exploit the catalogues of the Magellanic Clouds' variable stars provided by the EROS-2 and OGLE III/IV microlensing surveys. By combining these surveys, we present the currently widest-area view of the Large Magellanic Cloud as captured by the galaxy Cepheids, RR Lyrae stars and binaries. This reveals the full extent of the main structures (bar/s - spiral arms) that have only been vaguely guessed before. Our work strengthens the case for a detailed study of the Large Magellanic Cloud three-dimensional geometry.
748. M31C eclipsing binaries and Cepheids
ID:
ivo://CDS.VizieR/J/AJ/117/2810
Title:
M31C eclipsing binaries and Cepheids
Short Name:
J/AJ/117/2810
Date:
21 Oct 2021
Publisher:
CDS
Description:
We undertook a long-term project, DIRECT, to obtain the direct distances to two important galaxies in the cosmological distance ladder - M31 and M33 - using detached eclipsing binaries (DEBs) and Cepheids. While rare and difficult to detect, DEBs provide us with the potential to determine these distances with an accuracy better than 5%. The extensive photometry obtained in order to detect DEBs provides us with good light curves for the Cepheid variables. These are essential to the parallel project to derive direct Baade-Wesselink distances to Cepheids in M31 and M33. For both Cepheids and eclipsing binaries, the distance estimates will be free of any intermediate steps. As a first step in the DIRECT project, between 1996 September and 1997 October we obtained 95 full/partial nights on the F. L. Whipple Observatory 1.2 m telescope and 36 full nights on the Michigan-Dartmouth-MIT 1.3 m telescope to search for DEBs and new Cepheids in the M31 and M33 galaxies. In this third paper in the series, we present the catalog of variable stars, most of them newly detected, found in the field M31C [(RA, DE)=(11.10{deg}, 41.42{deg}), J2000.0]. We have found 115 variable stars: 12 eclipsing binaries, 35 Cepheids, and 68 other periodic, possible long-period or nonperiodic variables. The catalog of variables, as well as their photometry and finding charts, is available via anonymous ftp and the World Wide Web. The complete set of the CCD frames is available upon request.
749. M31 Cepheid disk sample of 1st year of PS1
ID:
ivo://CDS.VizieR/J/AJ/145/106
Title:
M31 Cepheid disk sample of 1st year of PS1
Short Name:
J/AJ/145/106
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a sample of Cepheid variable stars towards M31 based on the first year of regular M31 observations of the PS1 survey in the r_P1 and i_P1 filters. We describe the selection procedure for Cepheid variable stars from the overall variable source sample and develop an automatic classification scheme using Fourier decomposition and the location of the instability strip. We find 1440 fundamental mode (classical {delta}) Cep stars, 126 Cepheids in the first overtone mode, and 147 belonging to the Population II types. 296 Cepheids could not be assigned to one of these classes and 354 Cepheids were found in other surveys. These 2009 Cepheids constitute the largest Cepheid sample in M31 known so far and the full catalog is presented in this paper. We briefly describe the properties of our sample in its spatial distribution throughout the M31 galaxy, in its age properties, and we derive an apparent period-luminosity relation (PLR) in our two bands. The Population I Cepheids nicely follow the dust pattern of the M31 disk, whereas the 147 Type II Cepheids are distributed throughout the halo of M31. We outline the time evolution of the star formation in the major ring found previously and find an age gradient. A comparison of our PLR to previous results indicates a curvature term in the PLR.
750. M101 Cepheids
ID:
ivo://CDS.VizieR/J/ApJ/508/491
Title:
M101 Cepheids
Short Name:
J/ApJ/508/491
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on the identification of 255 candidate variable stars in a field located some 1.7' from the center of the late-type spiral galaxy M101 = NGC 5457, based on observations made with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope. Photometric measurements in the F555W and F814W filters - analyzed independently with the DAOPHOT/ALLFRAME and DoPHOT software suites - have been transformed to the Johnson V and Kron-Cousins I standard magnitude systems. Periods and intensity-averaged mean magnitudes for 61 carefully selected candidate Cepheid variables with periods in the range 10-48 days indicate a reddening-corrected mean distance modulus (m-M)_0_=29.05+/-0.14 (if the true modulus of the Large Magellanic Cloud is 18.50+/-0.10, and if there is no dependence of the period-luminosity relation on metal abundance); results consistent with this are obtained whether or not the sample is expanded to include a larger fraction of the candidates. Applying a metallicity-dependent correction of +0.16+/-0.10mag would increase this estimate to (m-M)_0_= 29.21+/-0.17mag.